This invention generally relates to electronic systems and in particular it relates to semiconductor image sensing devices.
Cross talk is a phenomenon that degrades the resolution of CMOS imagers at longer wavelength. Degradation in resolution manifests itself as blurring or reduction in contrast.
The origin of cross talk is the diffusion of photo-generated electrons from the neighboring pixels (receiving light stimulus) to pixels that are not supposed to receive light stimulus. Cross talk increases with incident light wavelength. This is due to the fact that: (1) longer wavelengths are absorbed deeper in the silicon, and (2) isotropic diffusion process from the absorption point looses the spatial information on light source.
An image sensor with improvements for suppressing cross talk without degrading red light response. This is accomplished by implanting a deep p+ layer under blue and green pixels but not under red pixels in a standard RGB pattern color filter array.